Preston - As a boy in the late 1960s, Joe Piela would marvel at the throngs of alewife that would swim into the brook that flowed beside the old mill that housed his grandfather's business, Piela Electric Inc.

"When I was a kid, it was so thick you could catch them with your hands," he said Thursday, as a Schumack Engineered Construction Co. workman on a backhoe did some final regrading around a newly constructed fishway at the brook. "They'd be jumping off the dam all night long. It was an amazing thing. But now you hardly see them."

Piela, now 55 and president of the company his grandfather founded, is among those eagerly awaiting the chance this spring to once again see the silvery fish fulfilling their migratory destiny as they swim into the brook to spawn. A nearly completed concrete-and-steel fishway under construction since September will enable alewife, also known as river herring, to swim into the stream variously named Hallville, Indiantown or Poquetanuck brook, and over the dam to spawn in Hallville Pond.

"This is going to pass a lot of fish," said Steve Gephard, supervising fisheries biologist in the Inland Fisheries Division at the state Department of Energy and Environmental Protection. "We've got a number of other fishways like this one, so we know that this will work."

Historically, he said, alewife would swim from Long Island Sound upstream into the Thames River, into Poquetanuck Cove and then into the brook, and continue to Avery Pond and Amos Lake to spawn. Over the years, many dams built along migratory fish routes blocked passage to favorite spawning areas, contributing to the decline of this important forage species. Alewife would still spawn in the brook below the dam, but not in the same numbers as before, Gephard said.

"They really want to spawn in ponds," he said. "Ponds smell different to them, because of the plants that grow there."

Piela recalled that Gephard first proposed building a fishway to his grandfather, also named Joe Piela, sometime in the 1970s. His grandfather liked the idea, but there was an obstacle.

"He would have had to allow access to the fish ladder through his building," Piela said. "But it was always in the back of everyone's mind."

In the late 1970s, an old storage building on the opposite side of the brook from the company's main building burned down, opening up that side. Then about eight years ago, Gephard revived the idea and turned to the Eastern Connecticut Conservation District to spearhead what would turn out to be a complicated project, involving multiple grant applications and working out design, engineering and legal issues to obtain an easement on the Pielas' property.

"We couldn't think of a reason not to do it," Piela said. "The timing was right."

Scott Gravatt, executive director of the conservation district, said this is the first fishway for his organization, which normally focuses on projects to improve or protect water quality. The $510,000 needed to build it was cobbled together from a $100,000 mitigation payment made to DEEP from the Fishers Island Ferry District for its dock expansion; $283,000 from DEEP's Long Island Sound license plate sales funds; $73,000 from the U.S. Fish & Wildlife Service; and $50,000 from the Natural Resources Conservation Service.

The fishway consists of a zigzagging concrete channel just below the dam, with a resting pool in the middle. As the alewife swim toward the dam, they will find their way into the channel, then swim up the gradual slope into the pond. DEEP staff will visit the fishway periodically in the spring to adjust equipment that regulates the water level to ensure there won't be too much or too little for the fish, Gravatt said. Just before they enter the pond, they will pass through a viewing chamber to be counted and recorded on video.

"We'll have a webcam, so classrooms can access it with an Internet connection," he said. "We're very excited about this project."

The completed project will include new fencing around the dam and a kiosk at the fish ladder to explain the fishway to visitors.

Next, Gephard said, DEEP would like to remove dams farther upstream so that the alewife can continue past Hallville Pond all the way to Amos Lake. This one, he said, will reach its peak migratory run in four years. That's how long it will take for the first fish born in Hallville Pond by the first adult alewife who make the pioneering run up the fishway to themselves reach adulthood and return to seed the next generation.

"Eventually, this will pass up to 100,000 fish a year," Gephard said. "We consider this to be a major achievement in terms of the Thames River habitat."